Thank you for your reply. Which siren, wired or wireless would be compatible?

Yes, you can connect an audible or visual siren to this device as it has an alarm output (Alarm Out). The siren can be triggered by corresponding events such as motion detection, line crossing or video failure. Whether the siren can also be triggered remotely via Hik-Connect is not explicitly described in the official data sheets - it is advisable to ask the manufacturer directly or check the current firmware, as remote control of alarm outputs is sometimes possible via the app, but is not guaranteed.